1. Field of the Invention
This invention relates to packet transmission in a network, and more specifically to NACK repetition in uplink (UL) packet transmission in a Universal Mobile Telecommunication System (UMTS) for improved uplink signal detection and reduced uplink signal power.
2. Background Information
Currently, the User Equipment (UE), e.g., mobile device, will use discontinuous transmission (DTX) in the acknowledge/negative acknowledge (ACK/NACK) field on the high-speed dedicated physical control channel (HS-DPCCH) if the UE fails to detect correctly the signaling on the high-speed shared control channel (HS-SCCH). The Node B (network device) must offset its ACK/NACK decision threshold so as to avoid erroneously detecting this DTX as an ACK, or else the packet will be lost. The effect of this is to increase significantly the transmit power required by the UE for the ACKs.
Documents R1-02-0917, “Reduction of HS-DPCCH power requirements”, Philips, R1-01-1199, “Improvement in power requirements for ACK/NACK signaling”, Philips, and R1-02-0042, “Further results on methods for reducing the power required for ACK/NACK signaling”, Philips, are all incorporated by reference herein, and proposed that the UE should continue to transmit NACKs in every HS-DPCCH sub-frame after reception of an high-speed downlink shared channel (HS-DSCH) packet for the duration of a timer. While the timer was running, the Node B would not have to offset its detection threshold, so the ACK power for any subsequent packets during this period could be much lower. However, this method is disadvantageous in that extra UL interference is generated if no HS-DSCH packets are transmitted while the timer is running. Node B detection performance will not be good if there is need to separately detect ACK, NACK, and also DTX state.